1. Field of the Invention:
The present invention relates to a wafer style butterfly valve, and more particularly an arrangement for retaining the insert within the valve body.
2. Brief Description of the Prior Art:
Butterfly valves are well known in the art. Also known are insert type butterfly valves. Examples of such an insert type butterfly valves are Jamesbury Series 815 and 830 Wafer Sphere valves. It is common to position a valve insert, such as a valve seat for a butterfly valve, in recess at the axial end of the through opening in the valve body which defines the fluid flow passage. As a result, this insert can be reached by detaching the adjacent conduit at the connecting flange.
When the adjacent conduit is connected to the valve body at their adjoining flanges, the insert is held within the valve body and pressed between the valve body and the adjacent conduit, and so is securely held in place. However, some means are necessary for retaining the wafer in place within the valve body before the attachment of the adjacent conduit. It has been known to drill matching bolt holes through the insert and into a shoulder of the valve body, and then to bolt the insert to the valve body via these matching holes. However, this technique has the shortcomings that the drilling of matching holes is time consuming and the resulting bolt heads extending from the insert may mar the surface of a gasket at the axial end of the insert. Moreover, the insertion and removal of the insert from the valve body requires bolting and unbolting, which is also time consuming.